In this second year of a longitudinal study of behavioral effects of exposure to inorganic mercury, inductrial workers will continue to be tested using objective tremor, electromyographic, and psychomotor tests. Primary emphasis is on detection of functional changes in workers who newly enter mercury exposure jobs, or transfer from exposure jobs to non-exposure areas. Workers who have thus been exposed to mercury and matched controls are tested at two mercury chlor-alkali plants at three month intervals. In previous work, frequency spectra obtained from measurement of forearm sustension tremor have been most sensitive in detecting early subclinical effects of mercury exposure. These effects have been found to be reversible upon removing the worker from mercury exposure. This research has the primary goal of demonstrating the use of behavioral testing methodologies as a part of medical management of workers exposed to neurotoxic substances.